This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. The ribosome [1] is a cellular machine that synthesizes proteins based on genetic instructions. The ribosome moves along the mRNA, catches tRNAs, facilitates the pairing between codons and anticodons, and catalyzes the formation of peptide bonds between amino acids. The bacterial ribosome is an important target of antibiotics;indeed, 50% of all research on antibiotics is focused on the ribosome. Currently the most successful approaches to image ribosomes are cryo-electron microscopy (cryo-EM) [2] and X-ray crystallography [3]. Cryo-EM offers insights into the function of the ribosome by providing snapshots of different functional states, currently at a resolution of 7 Angstroms. X-ray crystallography yields atomic-scale structural information for single or undefined functional states. These and other experiments show that the ribosome consists of two subunits, the small subunit being responsible for codon-anticodon recognition, and the large subunit for catalyzing peptide bond formation. The whole translation machinery consists of ribosomal RNAs, about 50 ribosomal proteins, tRNAs, mRNA, ions, and additional protein factors.